Expandable fusion cage system

ABSTRACT

An expandable fusion cage system includes an expandable fusion cage having an upper portion, a lower portion, and a hinge portion coupling the lower portion and the upper portion at their distal ends. Positioned between the upper and lower portions is an expansion element that when moved in the proximal direction causes the cage to expand at its proximal end. The system can also include inserter instruments, expandable distraction instruments, and bone funnels.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/774,038 filed Sep. 9, 2015, which will issue as U.S. Pat. No.10,039,650 on Aug. 7, 2018, which is a U.S. National Stage Filing under35 U.S.C. § 371 from International Application No. PCT/US2014/029214filed on Mar. 14, 2014, and published as WO 2014/144696 on Sep. 18,2014, which claims priority benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 61/799,412 filed Mar. 15, 2013, whichapplications are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

When posterior interbody fusion is performed (such as TLIF, OLIF or PLIFtechnique), it is difficult to insert a large enough fusion cage throughthe posterior access, especially when the disc space is significantlytaller anteriorly than posteriorly. Limiting factors include the maximumheight and width of the posterior access to the disc space, as well asthe risk of injuring the nerve roots or thecal sac that are immediatelyadjacent to the pathway of access to the disc. It is not uncommon for aposteriorly inserted fusion cage to fit reasonably tightly(appropriately sized) within the posterior portion of the disc space,but to be loose (undersized) with respect to the anterior portion of thedisc space. The inability to insert a properly sized fusion cage mayprevent the surgeon from obtaining as much lordosis in the fused segmentas desired, and may also increase the risk of post-operative migrationor retropulsion of the cage. Both situations may result in reducedefficacy of the surgical treatment.

Attempting to insert a larger fusion cage than the anatomicallimitations of the posterior access allow (in an attempt to avoid theproblems associated with an under-sized cage) may cause a number ofcomplications such as fracture of the vertebral endplates (which mayincrease the risk of implant subsidence), over-stretching of the nerveroots (which may result in temporary or permanent neurologiccomplications), “nicking” the nerve root or dura (which may result inCSF leakage or other neurologic complications), or fracturing theimplant due to overly aggressive impaction.

Other surgical approaches to the disc space (such as an ALIF or lateraltranspsoas approach) help alleviate some or all of the problemsidentified above, but may have other drawbacks. The most commonly usedapproach for interbody spinal fusion is the posterior approach, thus theother potential problems with these alternative surgical approachesoften outweigh the problem associated with the posterior access.

Some interbody fusion cages are designed to be inserted into the discspace on their sides, then rotated ninety degrees (90°) into the finalposition once inside the disc space. This allows an implant that is tallbut narrow to be inserted with less cephalad-caudal distraction of theanatomy during insertion. However, the tradeoff is that themedial-lateral width of these cages is larger during insertion.Especially in the case of very tall cages (such as a cage with a highdegree of lordosis), the anatomy may not accommodate the required cageheight when it is turned on its side for insertion. These “insert androtate” cages are also associated with other potential complicationssuch as inability to rotate the cage into final position (this rotationrequires some over-distraction of the disc space, which may not alwaysbe desirable or achievable), or fracture of the cage due to the twistingforces required to rotate the cage into position.

Other interbody fusion cages solve the problem by providing forexpansion of the implant after it is placed into the disc space. Theexisting art demonstrates a number of different designs for achievingthis, each of which has its own pros and cons.

SUMMARY OF THE INVENTION

The present disclosure is directed to spinal implants that areexpandable to provide adjustable lordosis, and surgical instruments foruse with the implants. This Summary is provided to introduce a selectionof concepts in a simplified form that are further described below in theDetailed Description. This Summary is not intended to identify keyaspects or essential aspects of the claimed subject matter. Moreover,this Summary is not intended for use as an aid in determining the scopeof the claimed subject matter.

These and other aspects of the present system and method will beapparent after consideration of the Detailed Description and Figuresherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention,including the preferred embodiment, are described with reference to thefollowing figures, wherein like reference numerals refer to like partsthroughout the various views unless otherwise specified.

FIGS. 1A-1C are a side, front end, and back end view, respectively, ofan expandable fusion cage according to various embodiments describedherein;

FIGS. 2A-2C are a top, perspective, and side view, respectively, of anexpandable fusion cage according to various embodiments describedherein;

FIGS. 3A-3C are a side cross sectional, top, and perspective view,respectively, of an expandable fusion cage according to variousembodiments described herein;

FIGS. 4A-4C are a side, side cross-sectional, and top view,respectively, of an expandable cage according to various embodimentsdescribed herein;

FIGS. 5A and 5B are partially see-through top views of an expandablefusion cage according to various embodiments described herein;

FIGS. 6A-6C are perspective, perspective see-through, and perspectivecross sectional views, respectively, of an expandable fusion cageaccording to various embodiments described herein;

FIGS. 7A-7C are side views of an expandable fusion cage according tovarious embodiments described herein;

FIGS. 8A and 8B are a top and top see-through view of an expandablefusion cage according to various embodiments described herein;

FIGS. 9A-9C are a top see-through, perspective, and perspective crosssectional view, respectively, of an expandable fusion cage according tovarious embodiments described herein;

FIGS. 10A and 10B are perspective views of a slider for use in anexpandable fusion cage according to various embodiments describedherein;

FIGS. 11A and 11B are perspective views of an expandable fusion cageaccording to various embodiments described herein;

FIGS. 12A and 12B are perspective views of a slider for use in anexpandable fusion cage according to various embodiments describedherein;

FIG. 13 is a side view of an expandable fusion cage according to variousembodiments described herein;

FIG. 14 is a side view of an expandable fusion cage according to variousembodiments described herein;

FIGS. 15A and 15B are perspective views of a slider for use in anexpandable fusion cage according to various embodiments describedherein;

FIGS. 16A and 16B are perspective views of an expandable fusion cageaccording to various embodiments described herein;

FIGS. 17A and 17B are front and back end views of a slider for use in anexpandable fusion cage according to various embodiments describedherein;

FIGS. 18A and 18B are front and back end views of an expandable fusioncage according to various embodiments described herein;

FIGS. 19A-19C are a perspective see-through, a perspective see-through,and a perspective view, respectively, of an expandable fusion cageaccording to various embodiments described herein;

FIG. 20 is a perspective view of an expandable fusion cage according tovarious embodiments described herein;

FIGS. 21A through 27 are various partial see-through top view of anexpandable fusion cage according to various embodiments describedherein;

FIG. 28 is a perspective view of an implant inserter according tovarious embodiments described herein;

FIG. 29 is a side view of the implant inserter shown in FIG. 28;

FIG. 30 is a top view of the implant inserter shown in FIG. 28;

FIG. 31 is a see-through perspective view of the distal tip of theimplant inserter shown in FIG. 28;

FIG. 32 is a close up top view of the implant inserter shown in FIG. 28;

FIG. 33 is a close up perspective view of the a portion of the implantinserter shown in FIG. 28;

FIG. 34 is a close up perspective view of the a portion of the implantinserter shown in FIG. 28;

FIG. 35 is a perspective view of an expandable distractor instrumentaccording to various embodiments described herein;

FIG. 36 is a perspective view of a mechanism included in the expandabledistractor instrument shown in FIG. 35;

FIG. 37 is a side view of the expandable distractor instrument shown inFIG. 35;

FIG. 38 is bottom view of the expandable distractor instrument shown inFIG. 35;

FIG. 39 is a bottom perspective view of the expandable distractorinstrument shown in FIG. 35;

FIGS. 40 and 41 are exploded view of the expandable distractorinstrument shown in FIG. 35;

FIGS. 42A and 42B are perspective views of a bone funnel according tovarious embodiments described herein; and

FIGS. 43 and 44 are perspective views of a bone funnel according tovarious embodiments described herein.

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

Embodiments are described more fully below with reference to theaccompanying figures, which form a part hereof and show, by way ofillustration, specific exemplary embodiments. These embodiments aredisclosed in sufficient detail to enable those skilled in the art topractice the invention. However, embodiments may be implemented in manydifferent forms and should not be construed as being limited to theembodiments set forth herein. The following detailed description is,therefore, not to be taken in a limiting sense. Moreover, the technologyof the present application will be described with relation to exemplaryembodiments. The word “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. Additionally, unless specificallyidentified otherwise, all embodiments described herein should beconsidered exemplary.

Expandable lumber interbody fusion (ELTF) cages, such as those disclosedherein, solve one or more of the above problems by providing the abilityto expand the cage to the desired anterior height. Because the posteriorend of the cage does not increase in height, this expansion increasesthe lordosis of the cage. Expansion of the cage is achieved by pushing awedge-like slider anteriorly, such that it wedges the anterior end ofthe cage apart.

With reference to figures IA through 20, the expandable fusion cage (orspinal implant) 100 can include an upper portion 110, a lower portion120, a hinge portion 130, and expansion element 140.

The upper portion 110 can include proximal end 111, a distal end 112,and a longitudinal axis LA1 extending therebetween. The upper portion110 can further include an opening 113 (shown in, e.g., FIG. 2A). Theopening 113 can extend longitudinally, and typically terminates prior tothe proximal end 111 and distal end 112.

The lower portion 120 can include proximal end 121, a distal end 122,and a longitudinal axis LA1 extending therebetween. The lower portion120 can further include an opening 123. The opening 123 can extendlongitudinally, and typically terminates prior to the proximal end 121and distal end 122. In some embodiments, the opening 113 and the opening123 are aligned.

Each of the upper portion 110 and the lower portion 120 includes anupper (outer) surface and a lower (inner) surface opposing the uppersurface. The lower surface of upper portion 110 generally faces thelower surface of the lower portion 120. The lower surfaces of the upperportion 110 and lower portion 120 are generally adapted to engaged theexpansion element 140. In some embodiments, the openings 113 and 123define a channel 150 between the upper portion 110 and lower portion120. In some embodiments, the expansion member 140 resides within thisslot 150 and can be moved distally and/or proximally within the channel150. In some embodiments, the distance between the lower surfaces of theupper portion 110 and the lower portion 120 decreases towards theproximal end 111/121 of the spinal implant 100. In this manner, movingthe expansion member 140 towards the proximal end 111/121 tends to causethe upper portion 110 and lower portion 120 to move apart at theproximal end (the distal ends of the lower 120 portion and the upperportion 110 tend to stay together because of the hinged portion 130).

In some embodiments, one or more slots can be defined by the lowersurfaces of the upper portion 110 and lower portion 120. With referenceto FIG. 3A, the spinal implant can include a first slot 161 and a secondslot 162. The spinal implant 100 can includes more or fewer slots. Theslots 161/162 are generally oriented perpendicular to the LA1. The slotsare shaped and sized so that they will engage with expansion member 140as it is moved in the proximal direction. In some embodiments, movingthe expansion member 140 into the first slot 161 increases the height ofthe proximal end a first distance and moving the expansion member 140into the second slot 162 increases the height of the proximal end asecond distance, with the second distance being greater than the firstdistance. The expansion member 140 can include one or more angledportions to engage the slots 161/162. For examples, as shown in FIGS.7A-7C, the expansion member 140 includes first angled portion 141 andsecond angled portion 142. In between the angled portions 141 and 142may be a relatively flat section which can allow the expansion member140 to “lock” into the first slot 161. A similar flat section may belocated distally from the angled portion 142 so that the expansionmember 140 may “lock” into the second slot 162.

In some embodiments, the expansion element 140 has a width equal to thatof the openings 113, 123 in the upper portion 110 and lower portion 120.In this manner, the expansion element 140 can be sized as tall as theoverall height of the implant 100, or even taller. In such embodiments,the taller expansion element is able to achieve a much greater increasein height and lordosis upon expansion of the implant.

The hinge portion 130 is generally located at the distal end of thespinal implant 100 and couples the upper portion 110 to the lowerportion 120 at their distal ends 112, 122. The hinge portion can have ahinge axis which is generally aligned perpendicular to the longitudinalaxis LA1 of the spinal implant 100. The hinged portion 130 allows thespinal implant to increase in height at the proximal end while remainingthe same height at the distal end to thereby achieve lordosis.

Many existing cage designs cannot provide sufficient strength for aposterior spinal fusion cage of appropriate size if manufactured fromPEEK. The upper and lower portions of spinal implant disclosed hereinincorporate a “living hinge” design, which allows bending within thehinge region via deformation of the material. In previously knownimplants using PEEK, it has been very difficult to find an appropriatebalance where the hinge provides sufficient flexibility to accommodatethe desired range of expansion (ideally in the 5°-30° range, with adesign goal of obtaining at least 15° of expansion or lordosis), whilealso providing enough strength and stiffness to meet the strengthrequirements for the device. In particular, it has been difficult toprovide a hinge design that accommodates the necessary amount ofexpansion while also providing an implant that is strong and stiffenough in compression-shear loading of the implant, and that also worksin a range of implant heights ranging at least from 8 mm to 14 mm inheight and preferably over an even wider range of heights. Hinge designsthat worked for a short implant (such as 7-8 mm tall) may not work for atall implant (such as 12-14 mm tall). Some designs worked in the shortimplant but did not provide enough flexibility in a taller implant andresulted in breakage at the hinge. Other designs worked in the shortimplant and provided enough flexibility for expansion in the tallerheights, but resulted in much lower shear strength or stiffness in thetaller heights. The implant disclosed herein solves this problem byadopting grooves as described below.

In some embodiments, hinged portion 130 includes an elongate groove 131on both the upper and lower portion of the implant. The elongate groove131 is formed in the outer surfaces of the spinal implant. As describedin greater detail below, the elongate groove 131 can provide the benefitof sufficient flexibility, strength, and stiffness.

The preferred implant material for the fusion cages 100 is PEEK polymer.In addition to being biocompatible, PEEK provides desired imagingcharacteristics post implantation. In some embodiments, the upperportion 110, lower portion 120, and hinged portion are integrally formedfrom a biocompatible plastic material such as PEEK.

As shown in, for example, FIGS. 3A and 3C, the expansion member 140 mayinclude a threaded recess 142. An insertion tool can be inserted intothe threaded recess 142 in order to engage the expansion member 140 andmove it in a direction towards the proximal end of the spinal implant100. In order to access this recess 142, the hinged portion 130 can alsoinclude a threaded passage 132 through which the tool can be inserted inorder to access the expansion member 140 positioned within the spinalimplant 100.

As shown in the Figures, the height of the unexpanded spinal implant 100can vary from the distal end to the proximal end. In some embodiments,the height gradually increases from the distal end before reaching apeak height near the proximal end, after which the height graduallydecreases.

One popular surgical technique used for posterior interbody spinalfusion uses a relatively straight implant (as opposed to an implant thatis highly curved in the axial plane), which is inserted in a straightpath at an oblique trajectory across the disc space. This approach isoften referred to as an oblique or OLIF technique. The typical obliquetrajectory is oriented approximately thirty to forty-five degrees(30-45°) away from a straight A-P orientation (i.e., angled away fromthe sagittal plane). This oblique approach differs from a traditionalPLIF approach in that PLIF cages are placed on a trajectory that iscloser to straight A-P orientation (roughly parallel with the sagittalplane). Also, PLIF cages are usually placed bilaterally on either sideof the anatomic midline, while the oblique approach more commonly useson a single cage placed across the disc space with the posterior portionon the ipsilateral side of the spine and the anterior portion resting onthe contralateral side across the anatomic midline. Most or all priorart expandable cages that provide anterior expansion of the cage toincrease lordosis incorporate a hinge axis that is perpendicular to thelong axis of the implant, thus at any distance along the length of theimplant the two sides (medial and lateral) are raised by the same amountof increased height as the anterior end of the cage is expanded. Ifthese implants are placed in a straight A-P orientation, then the hingeaxis for changes in lordosis is parallel to the coronal plane, andexpansion will give true sagittal-plane lordosis wherein both sides ofthe spine are distracted by the same amount. However, if these type ofimplants are placed with an oblique trajectory across the disc space,then the hinge axis will also be oriented at an angle from the coronalplane and thus expansion of the implant will tend to raise one side ofthe spine more than the other. This may introduce an imbalance to thespine that could result in an undesirable, iatrogenic coronal deformity.

Referring now to FIGS. 21A through 27, embodiments of the implantdescribed herein can be asymmetrical for use with oblique surgicaltechniques. Oblique implant 200 can include a hinge axis 210 that isoriented at a non-orthogonal angle to the longitudinal axis 220 of theimplant to match or generally match the oblique trajectory forinsertion. For example, models that are designed to be inserted at a 35°angle from the sagittal plane (i.e., 55° from the coronal plane) have ahinge axis that is also oriented 35° away from perpendicular (in otherwords, the hinge axis is oriented 55° from the long axis of theimplant). This ensures that when the implant 200 is placed along a 35°trajectory from the sagittal plane, that the hinge axis 210 operates inparallel with the coronal plane of the spine resulting in expansion thatprovides equal distraction to both sides of the spine and thus achievesproper spinal balance of the distracted segment. Other features of theimplant 200 are generally similar or identical to the features of theimplant 100 described above.

With reference now to FIGS. 28 through 34, the expandable fusion cagesdescribed herein can be used with inserter instruments capable of bothengaging the expandable cage and actuating the expansion element.

An inserter instrument 300 includes a shaft portion 310, a handleportion 320, and a trigger portion 330. A distal end 311 of the shaftportion is outfitted with a mechanism suitable for use in gripping theimplant 100. Inside of the shaft portion 310 is a rod capable of movingdistally and proximally through the shaft 310. In some embodiments, thetrigger portion 330, when squeezed, results in the rod 350 deploying outof the distal end 311 of the shaft a certain distance. The rod isaligned with the expansion member inside of the implant 100 such thatwhen it deploys out of the distal end 311, it engages the expansionelement and moves it towards the proximal end of the implant 100 tothereby cause expansion of the implant 100 at the proximal end.

The inserter instrument 310 can also include an adjustment feature thataccommodates different implant lengths while still providing consistencyof travel in the expansion element. Each implant length requires adifferent amount of travel to actuate the expansion slider. A positiongauge on the instrument is designed to measure correctly regardless ofimplant length. The expansion element distance is controlled to preventover-actuation (which might result in the expansion slider being pushedout the front of the implant, if not controlled), and the instrumentgrip ergonomics and tactile feedback to the surgeon is not changed withdiffering implant lengths.

With reference now to FIGS. 35-41, another instrument that can be usedwith the expandable fusion cages described herein is an expandabledistractor 400. The expandable distractor 300 (or trial instrument)provides an expandable tip 410 to distract and/or measure the disc spaceheight. Prior art examples of this type of expandable instrument mayincorporate an expansion mechanism that uses a sliding/rotatingbar-linkage design. However, the rotating nature of these bar-linkagemechanisms creates an inherent change in mechanical advantage, becomingmore powerful the further the instrument tip is expanded. Becausesurgeons rely heavily on tactile feedback to determine the appropriateamount of expansion (and to avoid complications such as overdistractionof surrounding soft tissues or inadvertent fracture of the vertebralendplates), it is undesirable to have the instrument's mechanicaladvantage (“power”) change over its range of travel. The expandabledistractor 400 described herein addresses this problem by incorporatinga second bar-linkage mechanism that offsets the mechanical function ofthe tip expansion mechanism 410. When the two mechanisms are combined,the second bar-linkage mechanism compensates for the changing mechanicaladvantage at the tip 410, so that the cumulative mechanical advantage ofthe overall instrument remains constant throughout the range of travelof the expandable tip 410.

With reference now to FIGS. 42A-44, various bone funnels are disclosedfor use in facilitating placement of bone graft within the disc spaceand within the implant. Prior art bone funnels use simple round tubeswith a cup-like member on the proximal end to hold the bone graft untilit is pushed through the tube into the disc space. In FIGS. 43 and 44, abone funnel 500 having a tapered tip 510 that docks into the opening atthe back of an implant 100 is shown. By docking directly onto theimplant 100, this funnel 500 improves ease of use in backfilling theimplant 100. Further, this funnel 500 is sized such that the openingthrough the bone funnel 500 is the same size as or slightly smaller thanthe opening at the back of the implant 100. Thus the surgeon is assuredthan any piece of bone graft material that is made small enough to fitdown into the funnel 500 will be small enough to fit through the back ofthe implant 100.

With reference to FIGS. 42A and 42B, a bone funnel 600 that uses a tube610 with a flattened shape rather than the typical round tube is shown.The flattened shape allows the cross-sectional area of the tube 610 tobe maximized (to maximize the size and amount of bone graft materialsthat can fit down through the tube 610) while maintaining the height andwidth of the tube cross-section equal or smaller than the cross-sectionof the smallest implant (thus ensuring that the bone grafting step doesnot require a larger window of access to the disc space than is requiredfor the implant, or cause over-distraction of the spine).

The various embodiments disclosed herein may offer one or more of thefollowing advantages:

The oblique implants can provide true sagittal-plane lordosis as theimplant is expanded, despite being placed at an oblique trajectoryacross the disc space.

The implants can provide multiple steps of distraction. For example, theexpansion element can include two seats of differing heights. When thesurgeon pushes the expansion clement forward until the first scatengages the locking features at the distal end of the implant, theimplant is expanded by a first incremental height, and the matinglocking features between the implant body and the expansion element seatensure that the in situ forces on the implant will not dislodge theexpansion element from that location (thus preventing collapse of theexpanded implant). If the surgeon desires more expansion, the expansionelement is advanced further until the second seat engages the lockingfeatures on the implant body. In this second expanded position, theimplant is expanded to a second height that is incrementally greaterthan the first expanded height (because the second seat is incrementallytaller than the first seat). The implant can accommodate an expansionelement with 1, 2, 3 or more steps of different height, providing 1, 2,3 or more different expanded positions, respectively.

Because of the hinge design described herein, the implants can provide alarger range of expansion. For a given disc height or angle of lordosis,the implant can achieve the necessary final expanded size with animplant that is shorter during insertion (in the unexpanded condition).

Many of the prior art designs use a screw or worm gear placed down themiddle of the implant. This interferes with space for bone graftmaterial and with cross-sectional area that can ultimately be filledwith a column of fused bone between the adjacent vertebrae. Becauselong-term stability of the fused spine is dependent on achieving a solidbony fusion, increasing the cross-sectional area available for bonygrowth is desirable. Various design described herein include arelatively small expansion element rather than a screw or othercomponent, which thereby provides a much larger area for bone graft andbony fusion.

Various implant embodiments described can allow the implant to bebackfilled with bone graft material after expansion, and the open sidesof the implant allow bone graft material to be extruded through theimplant and out into the surrounding region within the disc space, thusfilling in any gaps that may have been left and increasing theprobability of a successful fusion.

Various implant embodiments described herein are much more simple thanprior art devices, and can be more readily manufactured using standardmaterials and machining techniques resulting in a lower cost ofmanufacturing.

Various embodiments of the inserter instruments described herein providethe necessary function and safety limits on actuation within a singleinstrument, compared to prior art systems that require multipleinstruments to achieve the same result and may not provide the samelevel of safety checks on implant expansion.

Various embodiments of the expandable distractor/trial instrumentdescribed herein provide a constant ratio of input force or torqueversus expansion force on the adjacent vertebrae, as the tip isexpanded. Compared with prior art expandable instrument tips thatprovide progressively higher ratios of expansion force versus inputforce/torque, this instrument design provides an increased level ofsafety associated with the consistency of tactile feedback to the user.

Various embodiments of the bone funnels described herein are animprovement over the prior art. The ability of one funnel to securelydock to the implant (without the need for additional steps such asthreading into the implant, which would increase fiddle factor andpotentially decrease the amount of working space left after docking),which increases the ease of backfilling the expanded implant with bonegraft, is a benefit over prior art systems. The flattened shape of theother funnel, to maximize the cross-sectional area for bone graftdelivery while keeping the instrument profile within the minimum workingchannel required for implant insertion, represents an improvement overthe art.

The ability to extrude bone graft through the back of the implant andout the sides into the adjacent disc space area provides a benefit overthe art in terms of the likelihood of achieving a successful fusion.

The implant material can optionally be chosen to enhanceosseointegration between the implant and the living bone. For example,the components could be formed with a roughened surface texture or couldbe porous. To encourage ingrowth, PEEK components could be coated orembedded. PEEK, titanium or any other biocompatible material may provideadequate strength.

Although the technology has been described in language that is specificto certain structures, materials, and methodological steps, it is to beunderstood that the invention defined in the appended claims is notnecessarily limited to the specific structures, material s, and/or stepsdescribed. Rather, the specific aspects and steps are described as formsof implementing the claimed invention. Since many embodiments of theinvention can be practiced without departing from the spirit and scopeof the invention, the invention resides in the claims hereinafterappended. Unless otherwise indicated, all numbers or expressions, suchas those expressing dimensions, physical characteristics, etc. used inthe specification (other than the claims) are understood as modified inall instances by the term “approximately.” At the very least, and not asan attempt to limit the application of the doctrine of equivalents tothe claims, each numerical parameter recited in the specification orclaims which is modified by the term “approximately” should at least beconstrued in light of the number of recited significant digits and byapplying ordinary rounding techniques. Moreover, all ranges disclosedherein are to be understood to encompass and provide support for claimsthat recite any and all subranges or any and all individual valuessubsumed therein. For example, a stated range of 1 to 10 should beconsidered to include and provide support for claims that recite any andall subranges or individual values that are between and/or inclusive ofthe minimum value of 1 and the maximum value of 10; that is, allsubranges beginning with a minimum value of 1 or more and ending with amaximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and soforth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth).

What is claimed is:
 1. A spinal implant, comprising: an upper portionhaving a proximal end, a distal end, and a longitudinal axis extendingtherebetween; a lower portion having a proximal end, a distal end, and alongitudinal axis extending therebetween; and a hinge portion couplingthe upper and lower portion distal ends, the hinge portion having ahinge axis disposed transverse and at a non-orthogonal angle to both thelongitudinal axes of the upper and lower portions.
 2. The spinal implantof claim 1, wherein the hinge axis is disposed at an angle of betweenabout fifteen (15) degrees and about forty (40) degrees relative to thelongitudinal axes.
 3. The spinal implant of claim 1, further comprising:an expansion element disposed between the upper and lower portions, theexpansion element adapted for slidable movement between the upper andlower portions.
 4. The spinal implant of claim 3, wherein the expansionelement has a variable height along a length of the expansion element.5. The spinal implant of claim 1, wherein the upper and lower portionseach have an opening therethrough, and wherein the openings in the upperand lower portions are aligned.
 6. The spinal implant of claim 3,further comprising opposing surfaces defined by a lower surface of theupper portion and an upper surface of the lower portion, wherein theopposing surfaces are adapted to engage the expansion element.
 7. Thespinal implant of claim 6, wherein the opposing surfaces comprise atleast one slot adapted to engage the expansion element.
 8. The spinalimplant of claim 7, wherein the expansion element has an angled outersurface adapted to engage the at least one slot to alter an overallheight of the proximal ends.
 9. The spinal implant of claim 7, whereinthe opposing surfaces comprise at least two slots adapted to engage theexpansion element and provide at least two different overall separationamounts between the proximal ends.
 10. The spinal implant of claim 1,wherein the upper portion, lower portion and hinge portion areintegrally formed from a biocompatible plastic.
 11. The spinal implantof claim 1, wherein the hinge portion comprises: an elongate grooveformed in an outer surface of the upper and lower portions adjacent tothe proximal ends.
 12. The spinal implant of claim 1, wherein the hingeaxis transverse angle generally corresponds to a desired implantimplantation angle.
 13. The spinal implant of claim 1, wherein the hingeaxis is generally perpendicular to the sagittal plane when the implantis implanted between two adjacent vertebrae.
 14. A spinal implantsystem, comprising: a spinal implant as in claim 1; and an implantationtool for positioning the implant at a desired orientation and moving theexpansion element to a desired location between the upper and lowerportions.
 15. The spinal implant system of claim 14, further comprising:a bone growth promoting substance disposed between the upper and lowerportions.
 16. The spinal implant system of claim 14, further comprising:a funnel member for inserting a bone growth promoting substance in theimplant.
 17. A method of using a spinal implant, comprising: providing aspinal implant as in claim 1, inserting the implant between two adjacentvertebra at a desired angular orientation; and providing a desiredlordosis of the implant between the vertebra.
 18. The method of claim17, wherein the spinal implant further comprises: an expansion elementdisposed between the upper and lower portions, the expansion elementadapted for slidable movement between the upper and lower portions. 19.The method of claim 18, wherein providing a desired lordosis of theimplant between the vertebra comprises: moving the expansion element toa desired position within the spinal implant.
 20. The method of claim17, wherein the desired angle is transverse to the anterior-posterioraxis of the vertebrae, and wherein the desired lordosis is parallel tothe anterior-posterior axis of the vertebrae.